1. Field of the Invention
The present invention relates to a method for teaching a position of a semiconductor wafer to a semiconductor wafer carrying robot, and more specifically to an external teaching tool for use in the method.
2. Description of Related Art
Conventionally, in the same manner as in a general industrial robot, a teaching operation of a semiconductor carrying robot has been performed by an operator by guiding the robot to a wafer to be carried while visually recognizing the wafer position. In some cases, however, it is difficult, or even impossible, to visually recognize the wafer disposed in a processing equipment or the like from the outside thereof. Under the circumstances, a so-called automatic teaching method/apparatus for teaching a wafer position to a robot has been proposed. In such a method/apparatus, a teaching tool having the same size as that of an actual wafer is disposed in a processing equipment, etc., in place of a wafer and the position of the teaching tool is taught to the robot by detecting the teaching tool with a sensor mounted on the end effector of the robot.
The present inventors previously proposed a method for sensing a teaching tool using a hand having two transmission-type sensors (see, e.g., International Publication WO 03/22534). In a conventional wafer position teaching method, the operation for automatically moving a wafer gripping portion of the robot to the vicinity of the teaching tool to sense the teaching tool with the sensor mounted on the wafer gripping portion is performed based on the taught position (hereinafter referred to as “pre-taught position”) calculated from the device design drawing in advance. Also proposed by the present inventors was a method in which the operation for moving the wafer gripping portion to the vicinity of the teaching tool is performed manually (see, e.g., Japanese Unexamined Laid-open Patent Publication No. 2005-123261). In order to enhance the rate of automation to shorten the teaching operation time, it is preferable to move the wafer gripping portion automatically.
In a conventional method, however, if the installation accuracy of a processing equipment with respect to a robot is poor, in the case of equipment having a small inlet opening (hereinafter referred to as “frontage”), there is a problem that a wafer gripping portion may hit against the processing equipment when the wafer gripping portion approaches the teaching tool.